1. Field of Invention
This invention concerns water absorbent polymer articles and a process for their production. More particularly, the invention discloses a starch or cellulose-based water absorbent polymer combined with a foamable latex polymer to form a latex foam polymer containing a water absorbent polymer within its structure.
2. Prior Art
Recently there has been interest in producing absorbent materials particularly for use in products such as sanitary napkins, diapers, disposable dust cloths, etc. Some of the prior art materials used to form these products have been non-woven fabrics, papers, pulps, spongy urethane resins, natural sponges and the like. However, these materials exhibit relatively low water absorbency, thus failing to satisfy the need for a low volume, highly water absorbent material.
Substitutes for these materials such as cross-linked polyethylene oxides, cross-linked polyvinyl alcohols and hydrolyzed products of starch-polyacrylonitrile-grafted polymers have recently appeared on the market. While these products do show increased water absorbency, they also suffer from significant disadvantages in that their water absorbency is still not sufficiently high to justify their costs and difficulties of production. In addition, some of these materials create disposal problems because they are not biologically degradable.
Japanese Patent Application Kokai, No. 57-92,032 (1982) discloses a polyurethane foam that contains a useful water absorbent polymer wherein the size of the water absorbent resin is in the range from about 200 to 400 microns. This Kokai fails to disclose the combination of a water absorbent polymer with a latex foam.
U.S. Pat. No. 4,725,428 discloses a process for making a crosslinked, super absorbent polyurethane foam which contains a plurality of polycarbonyl moieties convalently attached to the polyurethane through at least one urethane, thiourethane or urea linkage. See also U.S. Pat. No. 4,725,629. However, neither of these patents discloses the combination of a water absorbent polymer with a latex foam.
A biodegradable, highly water absorbent polymer is disclosed in U.S. Pat. No. 4,076,663. While the resins of this patent do show increased water absorbency, their use has been limited to mixing them with sanitary napkins, diapers and other such products wherein the resins are used in their particulate or powder form. Thus, this process fails to disclose the use of this water absorbent resin within a confined structure or for use with other polymers within a latex foamed structure.
U.S. Pat. Nos. 4,454,268, 4,337,181 and 4,133,784 disclose various types of films partially comprised of water absorbent polymers. While these patents disclose starch-based, water absorbent polymers prepared from a combination of starch and ethylene acrylic acid copolymers, they fail to disclose the water absorbent polymer disclosed herein or the mixture of a water absorbent polymer with a conventional latex foamable polymer to form a latex foam which exhibits high water absorbency.
U.S. Pat. No. 3,669,103 discloses water swellable, water insoluble polymeric sorbents for the absorption of aqueous fluids wherein said polymeric sorbents are lightly cross-linked polymers. This patent discloses the use of a polyurethane foam as a support for the polymeric absorbent. However, it fails to disclose the use of a water absorbent polymer in general, the water absorbent polymer disclosed herein, or a latex foam support.
Latex materials, particularly latex foams have been well known for many years. The largest single use of latex today is in foam rubber. Latex foams are frequently used in mattresses, pillows, seat cushions, carpet backing and textile foam laminates. Latex foams also find use in providing cushioning in many types of fabrics such as athletic clothing.
There are numerous processes for the production of latex foams, because of their wide range of utility. See for example, U.S. Pat. Nos. 3,650,995, 4,205,103, and 4,174,415. While numerous latex foam patents exist, none discloses the use of a latex foam containing within its structure a cellulose based water absorbent polymer or a process for production of such a material.
Accordingly, it is an object of this invention to prepare latex foams containing within their structure water absorbent polymers.
It is a further object of this invention to disclose water absorbent latex foams which contain water absorbent polymers within their structure which are useful for the absorbance of fluids while retaining their shape.
It is a still further object of this invention to disclose a process for preparing latex foams containing water absorbent polymers which are secured to a backing to form a water absorbent latex foam laminate.
These and other objects, as well as the scope, nature, and utilization of this invention, will be apparent from the following detail description.